On 5 May 2001,
Beb Larkin, W7SLB, and Bob Larkin, W7PUA, completed a PUA43 mode
EME (Moonbounce) QSO on 2-meters using a single Yagi antenna at
each end and 150 Watts or less transmitter power. This is
believed to be substantially less station capability than has
been used for previous EME QSO's using any mode.

Circular
polarization was used with Yagis of boomlength 18 and 34 feet. A
total of 6-1/2 hours of transmission time was involved over 3
evenings. Call signs, grid squares and acknowledgments were
exchanged.

On the left is
Beb with the 18-foot K1FO style antenna arranged for circular
polarization. The hybrid coupler is hanging from the antenna and
Beb is holding the receiver preamp. All other equipment,
including the DSP-10, 8-Watt Brickette and 150 Watt amplifier
were inside the ham shack.

Here are the
top lines from the PUA43 screen of the DSP-10 transceivers
showing the copy. The differences in color are indicative of
difference in setup rather than better or worse copy. Note that
in one case the character (the 'U' in W7PUA) was in the
second-choice top row, rather than the primary bottom row. This
is allowable copy in the context of message estimation.

Much more
detail of the setups and operation is available in text
form.

Both
participants feel that it will be possible to streamline the
operation too reduce the time involved, or to reduce the power
levels even further by extending the time involved. Much still
needs to be demonstrated in DSP-aided QSO's.

Another
Picture: On the right is the 34 foot Yagi used at W7PUA. This is
a standard product from M2. There are 14 elements in each of two
planes that are at right angles. As the antenna is setup, the two
sets of elements are each at 45 degrees to either the vertical or
horizontal plane. A 5 foot insulated mast is hinged at the top of
the TV mast.

The hybrid
coupler for the antenna, receiver preamp and transmitter
amplifiers are all on the card table that is under the back of
the Yagi. The DSP-10 is inside, about 150 feet away. (Picture
added 9 May 01)

QRP 5-Watt 1296 MHz PUA-43 Mode EME QSO

On 25 February
2001 Ernie, W7LHL, and Larry, W7SZ, were successful with a PUA43
mode QSO on 1296 MHz EME (Moon bounce). They were using a QRP
power level of 5-Watts and backyard TVRO dishes of 10 and 12
feet.

Copy was Q5 as
can be seen on the screen at the left (click on it for a bigger
version). They were using a 28 character setting on PUA43 (see
below for more information on the PUA43 mode). The extra
characters were being used for redundancy in portions of the
message. The message would begin to appear in a few minutes, but
Q5 copy was taking roughly 15 to 30 minutes per message. They
exchanged call signs, grid squares, and confirmations both ways.
Copy at W7LHL was not quite as good as for the other direction,
but both stations received a complete message in the 28
characters. This was their first attempt at using the 5-Watt
level for a QSO. As was reported earlier they had been successful
at higher power during January.

None of those
involved are aware of any previous 5 Watt 1296 MHz EME QSO's
although this may well have been done using larger antennas. Any
information on this would be appreciated.

The PUA43 mode
described below is ideal for this type of work. The limits of
signal strength have yet to be fully explored. Both Ernie and
Larry reported that they were kept busy with antenna pointing and
playing screen "anagrams," so were not sure what their
patience level might be if the power kept dropping. The nature of
the mode is to trade-off time for increased sensitivity.

W7LHL Receives 10 GHz 1.2-Watt Self Echoes

On 17 February
2001, Ernie Manly, W7LHL was successful in receiving his own
echoes off the Moon at 10.368 GHz. This is quite commonplace
these days for the advanced microwave experimenter, but Ernie's
success was important because he he was running only 1.2 Watts
and using a 10 ft TVRO parabolic dish. The key to making this
work was the long-term integration capability of the EME-2 mode
in the DSP-10 transceiver.

A few
calculations show that the received signal strength should have
been about -165 dBm. This would be roughly 20 dB below the level
that can be heard with the ear. The measured returns have been
about 7 dB below the -165 level. The measured system Noise
Temperature was about 180 K. It must be that the assumed 50 per
cent efficiency for the parabolic dish is not accurate or that
reflection coefficients are not accurate or perhaps other
factors.

On 20 February
2001, Ernie made further EME-2 measurements as shown here. The
long-term (about 18 minute) integrated, relative S+N, response is
the yellow trace with the distinctive double peak. It is at a
scale of 0.1 dB/division. The results are interesting in terms of
not only receiving his signal, but in measuring the spectrum of
the return. From terrestrial contacts with other stations, the
spectrum of Ernie's transmitter and LO are known to be quite
clean. Therefore, the measured spectrum represents the Doppler
spreading of the EME path. The bandwidth of the FFT was 9.4 Hz
and this will broaden the apparent spectrum by about this amount.
But what was observed was sufficiently wider for this to not be a
major factor. The plot above is the top part of the DSP-10 screen
(the bottom of the waterfall continues as shown---there is not
much to see!) Libration-caused spectral spreading has been
observed by all 10 GHz EME operators, but it is interesting that
Ernie was able to get useful measurements of this effect at the
low power level.

The graph to the left
shows the results of some calculations that I (W7PUA) did with
Ernie's data. Starting with the measured (S+N)/N in each bin, I
used the measured noise temperature of 180 degrees to estimate
the return signal power spectral density. This gives a plot with
less effect from the noise. But, a signal of -180 dBm is noisy
and the results should be considered tentative until more power
is available. But, the general levels and the double-peaked shape
were reported by Ernie as quite repeatable. A possible
explanation for the particular shape is that the beamwidth is
slightly smaller than the moon (maybe 0.4 and 0.55 degrees) and
Ernie reported that he was keeping the antenna beam centered by
peaking on Moon noise. He would let the Moon drift to the edge of
his beam and then correct it, sometimes moving a bit ahead. Quite
possibly what is being seen is the Doppler due to libration
sometimes towards one side of center and sometimes towards the
other side. Depending on the distribution of time in each area,
the spectrum would be shifted that way. Also note that the
average spectrum is offset by about 20 Hz to the right. It is
known from many 1296 measurements that the Doppler routines in
the DSP-10 Rev 2 software have typical errors of 1 to 2 Hz at
that frequency which would be 8 to 16 Hz at 10368 MHz. This is
likely a large part of the shift, but further investigation is
needed. By the way, if you add up all the power (in Watts, not
dBm) you get -171.9 dBm total received power.

W7LHL 10 GHz EME-2 Update

Bigger
Signals! As a follow up to the 10 GHz EME-2 work described
above, Ernie, W7LHL, did further experimentation with
self-echoes. The received signal level was increased close to 10
dB by increasing the transmit power to 4 Watts, waiting for Moon
perigee, and possibly other factors such as increased skill at
Moon tracking. The screen shot from Ernie shows the waterfall
results for several tests. The yellow, long-term integration
trace at the top is the result of only the bottom part of the
waterfall starting just below the mark "49:33_". Note
that the scale for this yellow trace is 1 dB/division, whereas it
was much more expanded in the earlier experiment above (this is
automatically scaled to expand the trace without going off the
screen). The maximum averaged (S+N)/N is 2.6 dB in the center
bin. A constant RIT of 29 Hz was used to correct for errors in
the Doppler calculations, with the result that the spectrum is
centered. The same 10-foot dish and receiving setup was used as
for the original experiments.

As shown here,
I again calculated the signal-only spectrum, based on the assumed
system noise temperature. Three peaks are seen on this spectrum
and again the overall width is roughly 60 Hz. The overall total
received power is calculated to be about -162 dBm.

Based on
experience, the signal levels that Ernie is receiving should be
adequate for easy QSO's using the PUA43 mode. He has not
attempted this yet. (Posted 15 Mar 01).

W7LHL and W7SZ Have 10GHz EME QSO Using PUA43

On 11 November
2001, Ernie Manly, W7LHL, and Larry Liljeqvist, W7SZ, completed a
PUA43 mode EME (Moonbounce) QSO on 10368 MHz. Both stations were
using 10 foot surplus TVRO antennas. Ernie was running 5 Watts
and Larry, 15 Watts. This was their first try at such a QSO and
the total elapsed time was about 45 minutes. The contact was
important to evaluate the effects of dispersion that broadens the
signals and makes the received frequency less well defined. The
signals were far below the audible level throughout the QSO. This
is believed to be the first PUA43 EME contact on 10 GHz.

Here are the
top lines from the PUA43 screen of the DSP-10 transceivers
showing the copy. In both cases the calls and grid squares were
sent twice within a 28 character field. Copy was complete when
the message had been received in at least one of the two
transmitted positions. This is analogous to CW reception where
the operator waits until the full message is received, even
though it is not in a single contiguous group. Note that the
stations had doubled up the message in two different ways. W7SZ
use the first 14 characters for a full message with a repeat in
the second 14 characters. W7LHL doubled up the characters
throughout the message.

Both stations
were using the DSP-10 with an external 10 GHz GPS-locked Shera
frequency reference. Both used DB6NT transverters that were also
locked in frequency. W7LHL used a solid-state 5-Watt amplifier
and W7SZ ran 15 Watts output from a TWT amplifier. For both
stations the microwave equipment was located at the feed for the
parabolic antenna.

The Moon was
near South for both stations resulting in the spectral dispersion
being at its greatest. Angles to either the East or West would be
expected to produce superior copy. In spite of this level of
dispersion, the contact was made without difficulty.

In order to measure the
signal being received from the Moon, both stations operated both
before and after the QSO in the EME-2 mode. This automatically
transmits 2-second pulses every 5 seconds. These are aligned in
frequency according to the calculated Doppler shift and long-term
power integration is used to reduce the affects of noise. At the
left is W7LHL's EME-2 echo spectrum, with the last return in
white at 2 dB/div and the power average of 123 returns in yellow
at 0.5 dB/div. The resolution bandwidth is 9.4 Hz and the signal
in this bandwidth is about 5.6 dB below the noise. The display
shows (S+N)/N power which is just over 1 dB at the center of the
yellow trace. Clicking on the trace shows a larger portion of the
DSP-10 screen for this same measurement. Due primarily to the
higher power used, the spectrum of the EME-2 trace received
by W7SZ has a peak (S+N)/N of about 2.8 dB, placing the
peak signal and noise at almost equal levels.

Congratulations
to Ernie and Larry for building the stations and making the QSO!

More
weak-signal results using the DSP-10 will be posted as they
become available. Email these to boblark 'at sign' proaxis.com
and I will try to put them here.